lecture16 101021 - effect was a part Electrons sometimes...

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8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 0 1 2 3 4 5 Exam 2 Class Average = 14 Number of Students Score/20 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 Improvement in score from Exam 1 Light is a Wave, so What’s this about Photons? The Need for Quantum Mechanics s Photoelectric Effect s Emission of electrons by an illuminated metal s Blackbody Radiation s The electromagnetic radiation emitted by a heated object Classical physics Quantum mechanics (1920’s-) Relativistic mechanics, El.-Mag. (1905) Relativistic quantum mechanics (1927-) v / c hs Photoelectric Effect s When light is incident on certain metallic surfaces, electrons are emitted from the surface s The effect was first discovered by Hertz s The successful explanation of the effect was given by Einstein in 1905 s Received Nobel Prize in 1921 for paper on electromagnetic radiation, of which the photoelectric
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Unformatted text preview: effect was a part Electrons sometimes are Emitted from a Metal when Light Shines on the Metal Photoelectric Effect Schematic s When light strikes E, photoelectrons are emitted s Electrons collected at C and passing through the ammeter are a current in the circuit s C is maintained at a positive potential by the power supply light I V _ + e-Photoelectric Effect (I) No electrons were emitted until the frequency of the light exceeded a critical frequency, at which point electrons were emitted from the surface! (Recall: small b large ) electrons emitted ? No Yes, with low KE Yes, with high KE Increase energy by increasing amplitude Classical Method electrons emitted ? No No No No...
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This document was uploaded on 05/29/2011.

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